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# AQA D1 finding final edges of prims and kruskals Watch

1. I'm stuck on the following question:
2b(i) and 2b(ii)

For only 3 marks I have to find the 2 final edges for these 2 situations. Since it's only 3 marks my usual method of performing the whole algorithm is not very time effective and it may lead to me missing marks later on in the paper. I'm certain there's an easier way to find the final edges here without doing the entire algorithm.

What is the preferred method of doing this since I know the examiner isn't expecting me to do the whole algorithm on the table twice for just 3 marks.

Here is the untouched table,

And here is the table I achieved from question 2ai) which I think it expects me to use:

How would I go about answering question 2b(i) and 2b(ii) using this information the best way?
2. (Original post by Sayless)
How would I go about answering question 2b(i) and 2b(ii) using this information the best way?
Since there is a unique minimum spanning tree, you know which edges are going to make it up.

With Prim, I can't see any way of avoiding using the algorithm again, but bear in mind you're only going to be using certain edges, so you only need to check very few at each stage.

With Kruskal, you add edges of increasing weight, so the last one added will be the heaviest, so to speak.
3. (Original post by ghostwalker)
Since there is a unique minimum spanning tree, you know which edges are going to make it up.

With Prim, I can't see any way of avoiding using the algorithm again, but bear in mind you're only going to be using certain edges, so you only need to check very few at each stage.

With Kruskal, you add edges of increasing weight, to the last one added will be the heaviest, so to speak.
Thank you for explaining it so clearly, I understand it now, the unique minimum spanning tree part didn't even register to me, I know what I'm doing now

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